1. Field of the Invention
This invention relates generally to a cooling system for electronic devices. More particularly, this invention relates to a cooling system having a fan of a new configuration arranged to produce a cooling airflow passing through a novel flow-field with reduce turbulence, lower noise and high cooling efficiency.
2. Description of the Prior Art
One of the major limitations to further improve the performance and configuration design of the modern electronic devices is a requirement of heat removal and temperature control of the electronic devices. The heat removal design of an electronic device according to a temperature control requirement imposes space limitation and power supply requirement. Additionally, if a fan is employed, the noise generated from the operation of a fan must also be controlled and reduced.
The demand for improving the heat removal system is ever increased as the electronic devices become further miniaturized and the electronic circuits are manufactured with ever-increased density and required for operation at higher speed and consuming less power. As the electronic circuits are more densely integrated, higher rate of heat generation per unit volume is required for removal. On the other hand, a more stringent temperature control is necessary because the performance of the electronic circuits with higher performance levels tend to be more temperature sensitive. In the meantime, this more stringent temperature control requirement has to be satisfied with smaller spaces available for placement of the cooling system because now the electronic devices and also the air-moving devices are further miniaturized.
The most direct consideration for improving the heat removal performance for an air moving device is to consider the fan and the cooling airflow passing through the electronic circuits for removing the heat. FIGS. 1A and 1B shows a fan that is most commonly employed in cooling the electronic devices. The directions of the inlet and the outlet of the airflow are arranged in parallel. The blades of the fan are rotated along an axis perpendicular to the plane of the blades and in parallel to the airflow direction. This configuration produces a direct pressure difference between the inlet and outlet of the airflow thus provides large airflow for cooling and removing the heat generated from the electronic circuits. This configuration however results in several difficulties. The first difficulty is its inflexibility in arranging the cooling system. Optimal space arrangement may be difficult due to the need to arrange the inlet and outlet of the flow to direct the airflow to the electronic circuits. Additional difficulties are caused by the turbulent characteristics generated in the flow field. The rotation of the fan blades generates a turbulent flow not only in the air near the fan blades but also the turbulent characteristics are propagated to the entire airflow path from the inlet to the outlet of this cooling system. The turbulent characteristics in the flow field affect the stability of the airflow, the efficiency of the fan operation and also cause the noise to increase.
Therefore, a need still exists for a new system configuration and design method in the art of cooling system applying a fan and the airflow ducts to resolve these difficulties and limitations. More particularly, this new system configuration and design approach must be able to reduce the turbulence of the flow-field in the airflow path. By reducing the turbulence of the flow-field, more stable and smooth airflow is generated at higher fan efficiency. Furthermore, the noise of the fan can be reduced when the turbulence of the flow field is reduced.